Question

I am doing my project in xcode 4.2 (Older Version). For my application, I just set the variables, arrays in dto class for using in entire app lifecycle. so I set with a property like this.

AppDTO(sub class of NSObject)

AppDTO.h

@property(nonatomic,retain)anotherAppDTO *aAppDTO;
@property(nonatomic,retain)NSMutableArray *array1;
@property(nonatomic,retain)NSMutableArray *array2;
@property(nonatomic,retain)NSString *string1,*string2,*string3;

AppDTO.m

- (id)init
{
    self = [super init];
    if (self) {

    self.aAppDTO = [[anotherAppDTO alloc]init];
    self.array1 = [[NSMutableArray alloc]init];
    self.array2 = [[NSMutableArray alloc]init];

    self.string1 = @"Hello";
    self.string2= @"Hai";

    }
}


-(void)dealloc
{
    if(array1 != nil)
    {
        [array1 release];
        array1 = nil;
    }

    if(array2 != nil)
    {
        [array2 release];
        array2 = nil;
    }

    [aAppDTO release];
    aAppDTO = nil;

    [super dealloc];
}

when I analyze my app in Xcode 4.3.2, I get memory warning in self.array1 and self.array2 (Potential leak on object allocated on line….), but when I change self.array1 to array1, warning goes away.

What is the reason for using self. do I need to use self if I set @property(nonatomic,retain) to variables(like array1,array2,string1,string2).

Also in dealloc method, I heard we don’t want to use [self.array1 release], instead we can use [array1 release]. Is it Correct?

Do I need to release my string in dealloc method.

Also I am releasing aAppDTO in dealloc method. if I allocate some objects in anotherAppDTO class, will it release automatically when I call [aAppDTO release] method.

Can anyone clarify me.

Many Thanks,
Anish

Answer 1

You get the warning because when you write :

self.array1 = [[NSMutableArray alloc]init];

is the same as :

[self setArray1: [[NSMutableArray alloc]init]];

As you can notice you are not allocating the underlying array1 private variable, but you are calling the setter of the property that since it is declared as retain it retains the object once assigned, this means that when you eventually will assign another object the second time with the setter the first object will remain with a retain count of one until the application will be closed (since you don’t have any reference to that object anymore …) .

Take a look at this great article to understand better Manual Reference Counting in Objective-C .